This application claims the benefit of Korean Application No. 2002-32524, filed Jun. 11, 2002, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a method of detecting toner depletion in an image forming apparatus, and more particularly, to a method of detecting toner depletion in an image forming apparatus having an improved structure, in which toner low and toner depletion states are detected without using an additional detection sensor.
2. Description of the Related Art
In general, image forming apparatuses using toner form an electrostatic latent image corresponding to a desired image by scanning light on a photosensitive body, develop the electrostatic latent image by supplying toner to the electrostatic latent image from a developing unit in which toner is received, transfer the developed electrostatic latent image onto paper, and fuse the transferred electrostatic latent image on the paper, thereby forming an image.
In such image forming apparatuses, it is possible to detect whether toner that is received in the developing unit is exhausted and to inform a user of the toner depletion, and the concentration of a developer needs to be properly adjusted so as to improve the efficiency of the developer.
FIG. 1 illustrates a conventional apparatus to detect the amount of toner remaining in a developing unit. As shown in FIG. 1, a sensing unit 120 is formed in a lower portion of a developing unit 100 and has an uneven shape, and transparent windows 121 are placed on the right and left sides of the sensing unit 120, respectively. A detection sensor 130, outside the developing unit 100, includes a light emitting unit 131 and a light receiving unit 132. The transparent windows 121 are placed between the light emitting unit 131 and the light receiving unit 132.
In addition, an agitator 110, having a shaft 111 and a wing 112, is installed in the developing unit 100. The agitator 110 distributes toner uniformly while rotating in the developing unit 100, and rubs and charges the toner to prepare for image development.
If the wing 112 passes through the sensing unit 120 while the agitator 110 rotates in the developing unit 100, the toner adhered to the transparent windows 121 is cleaned, and then, the toner is pushed into the sensing unit 120. This is done to prevent sensing errors, which may be caused by toner adhered to the transparent windows 121 by static electricity and moisture. Such errors cause the sending unit 120 to detect toner even when toner does not remain in the developing unit 100.
Because of the above structure, light emitted from the light emitting unit 131 passes through the toner of the sensing unit 120 and is detected by the light receiving unit 132. In this case, the amount of light detected by the light receiving unit 132 depends on the amount of the toner remaining in the sensing unit 120. Hence, after the relation between the amount of light detected by the light receiving unit 132 and the amount of toner remaining in the sensing unit 120 is experimentally obtained, the amount of toner remaining in the developing unit 100 can be calculated using the experimental result.
However, the conventional apparatus to detect the amount of toner remaining in the developing unit 100 shown in FIG. 1 detects the amount of toner remaining only in a partial region of the developing unit 100, i.e., only in the sensing unit 120. Thus, the conventional apparatus shown in FIG. 1 determines that the toner is exhausted and displays a toner depletion message if toner does not remain in the sensing unit 120, even when toner remains in another region of the developing unit 100. Hence, a user cannot rely on the toner depletion message. Also, an additional detection sensor 130 should be provided, and thus overall costs of the apparatus increase.
In addition, even though the agitator 110 cleans the transparent windows 121 while rotating in the developing unit 100, when an image forming apparatus does not perform a print operation and is in a print standby state for a long time, or when the image forming apparatus is turned off for a long time and thus toner adheres to the transparent windows 121, the agitator 110 may not completely clean the transparent windows 121. In this case, although toner is completely exhausted, it may be determined by the detection sensor 130 that toner remains in the sensing unit 120.
In another method of detecting toner depletion in an image forming apparatus, the number of pixels printed from an initial time when the developing unit is used is counted without using the detection sensor shown in FIG. 1, and a toner depletion message is displayed if the number of pixels reaches a predetermined value. This method can be used only if the amount of toner required to print one pixel is uniform. However, the amount of toner that is actually used varies according to the concentration of an image printed even when the same number of pixels is printed. Thus, in the above method, the accuracy of detecting toner depletion is poor.
Accordingly, it is an aspect of the present invention to provide a method of detecting toner depletion in an image forming apparatus, in which a toner low state or a toner depletion state is detected by counting the number of pixels of a printed image without using an additional detection sensor, and by periodically detecting the concentration of the printed image.
Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
The foregoing, and/or other aspects may be achieved by providing a method of detecting toner depletion in an image forming apparatus which includes a photosensitive medium, a laser scanning unit to scan light on the photosensitive medium and to form an electrostatic latent image thereon, a developing unit to supply toner to the electrostatic latent image and thereby form a toner image, and an image controller to control the forming of the toner image. The method includes comparing an accumulation pixel number Qt obtained by accumulating and counting a number of pixels of the formed image with a reference pixel number Qr, calculated from an amount of toner initially received by the developing unit, and recognizing that the image forming apparatus is in a toner low state if the accumulation pixel number Qt is larger than the reference pixel number Qr, comparing a concentration of the formed image with a reference concentration Dr and detecting a toner depletion state if it is recognized that the image forming apparatus is in the toner low state; determining whether the developing unit is reinstalled; and determining whether the developing unit is a new developing unit, if it is determined that the developing unit is reinstalled.
The reference pixel number Qr may be set to be smaller than a quotient obtained by dividing the amount of toner that is initially received in the developing unit by the amount of toner required to print one pixel.
The method may further include detecting whether the amount of toner received in the developing unit is in a toner low state or a toner depletion state, if the image forming apparatus is turned on. The detecting includes checking a toner depletion state variable TE stored in the image controller and detecting whether the image forming apparatus is in the toner depletion state, and checking a toner low state variable TL stored in the image controller, and detecting whether the image forming apparatus is in the toner low state.
The comparing of the concentration may include forming a test patch to measure the concentration of the formed image printed per a predetermined print number Pr1; detecting the image concentration Di from the test patch, and comparing the image concentration Di with the reference concentration Dr, recognizing that the image forming apparatus is in the toner depletion state if the image concentration Di is lower than the reference concentration Dr, and forming another test patch if it is determined that the image concentration Di is not lower than the reference concentration Dr.
The test patch may have at least three different toner coverages. Also, the image concentration Di can be detected from the test patch that is formed on the photosensitive medium and can also be detected from the test patch that is transferred onto a transfer medium onto which the toner image formed on the photosensitive medium is transferred.
The forming of the test patch and the comparing of the image concentration may be repeated and it is recognized that the image forming apparatus is in the toner depletion state if the image concentration Di is lower than the reference concentration Dr, and the forming of the test patch is again repeated if the image concentration Di is not lower than the reference concentration. The comparing of the image concentration may include adjusting development variables so that the image concentration Di is the same as the reference concentration Dr when the method repeats the forming of the test pattern. The adjusting of the development variables may include applying a development bias voltage to a developing roller installed in the developing unit to supply the toner to the photosensitive medium, and/or adjusting an optical output of the laser scanning unit to scan light on the photosensitive medium and to form the electrostatic latent image.
The determining whether the developing unit is new includes detecting whether the developing unit is reinstalled, forming a test patch for measuring the concentration of an image printed per a predetermined print number Pr2, detecting the image concentration Di from the test patch, and comparing the image concentration Di with the reference concentration Dr, resetting the accumulation pixel number Qt to xe2x80x9c0xe2x80x9d and repeating the comprising of the accumulation pixel number if the image concentration Di is not lower than the reference concentration Dr, and repeating the comparing of the formed mage if the image concentration Di is lower than the reference concentration Dr.
In the comparing of Di with Dr, the determining whether the developing unit is reinstalled, the forming of the test patch, and the image concentration from the test patch are repeated (m) times. Furthermore, the accumulation pixel number Qt is reset to xe2x80x9c0xe2x80x9d and the method returns to the comparing of the accumulation pixel number if the image concentration Di is not lower than the reference concentration Dr, and the method returns to the comparing of the concentration of the formed image if the image concentration Di is lower than the reference concentration Dr. Also, the comparing of the image concentration is repeated (m) times, and it is recognized that the image forming apparatus is in the toner depletion state if the image concentration Di is lower than the reference concentration Dr.
According to the above method, errors of detecting toner depletion can be minimized in consideration of the number of pixels of an image printed and the concentration of the image.